In the area of pressure gauge calibration, a gas pressurizing pump is usually used as a pressurizing apparatus with a pressure calibration instrument. A gas pressurizing apparatus is a kind of widely used product in the area of pressure gauge calibration wherein air pumps generate required pressure by air compression, so that pollution and contamination to the environment happen in liquid pressurizing devices but hardly happen in air pumps. However, air pumps in the prior art usually employ one-stage gas compression for generating gas pressure, so that it can only reach a very low pressure depending on the compression ratio. In addition, depending on the operating forces, the gas pressurizing efficiency is so low that it will directly impact the efficiency of the pressure instrument's calibration. With the development of science and technology, bearing capacity of industrial pressure equipment has been improved, and the scale of the pressure monitoring instruments have been widened, too. Nevertheless, the pressurizing capability (value and efficiency) of air pumps applied to the calibration in the prior art is far from enough to meet the requirements of industrial development. Moreover, portable pressurizing devices are required for the on-site verification and calibration of the instrument. Therefore, it is urgently demanded for a kind of gas pressurizing apparatus which is light, easy to carry and to reach high pressure output.